Matt Wolf's mesmerizing, scrapbook-style docu conveys how the world developed the idea of the teenager

It’s hard to reconcile, considering the degree to which adolescents now dominate popular culture, but the idea of the teenager is a uniquely 20th-century invention, born out of advances in psychological theory, changes in child-labor laws and a boom in leisure-time activities for the under-20 set. A feat of both editing and blurring-of-the-edges nonfiction technique, Matt Wolf’s mesmerizing, scrapbook-style “Teenage” conveys the transition in how the world perceived this emerging in-between stage via a series of first-person portraits of exceptional individuals set amid a whirlwind of vintage footage. Ironically, the demo in question seems least likely to appreciate the pic’s arty, innovative approach.

The conventional thinking goes that until roughly World War II, society and scientists alike thought of life as two distinct stages, divided between children and adults. The former were patronized and sheltered up to a certain point, then shuffled off to work in factories at a young age. In the introduction to his paradigm-shifting book, Savage reveals that his initial research into the subject began as background for a possible television series, suggesting that he always intended a multimedia approach to the topic.

Eschewing the traditional TV documentary style, Wolf innovates a radically different format for the material, blending archival artifacts with invented elements to create an intimate, far more personal history of the emerging demographic across the four decades between 1904 and 1945, when Elliot E. Cohen published his young person’s manifesto, “A Teen-Age Bill of Rights,” in the New York Times. Though much of the footage has a stock newsreel feel, “Teenage” is clearly intended to suggest a homemovie record of its era. To that end, Wolf interweaves staged, retro-styled scenes of various characters to foster the illusion of a candid look at various youthful cliques of the time, ranging from London’s Bright Young People to the anti-Hitler “Edelweiss Pirates.”

Pic’s most obvious innovation is the absence of a dry, all-encompassing narrator, replaced by four voiceover actors hired to read excerpts from journal entries of the period (embellished with original dialogue designed to match elements from the filmmakers’ research). Jena Malone performs an early-century American girl, Ben Whishaw represents the British youth, Jessie Usher captures the unease of African-American teens and Julia Hummer plays a German fraulein whose lines were excerpted from Melita Maschmann’s chilling Nazi-era memoir, “Account Rendered” — each directed to sound distractingly contemporary.

When combined with the vintage (or vintage-styled) visuals, these recitations produce an almost Terrence Malick-like effect, contrasting personal impressions with the more objective, journalistic imagery presented onscreen. As a work of sociological history, “Teenage” withholds too much context to be of use, overemphasizing the European side of what it calls “an American invention.” As a thought experiment, however, it is uniquely crafted to inspire auds to muse on how the experience of adolescence must have felt at a time cusp-of-modern moment when engaged and driven young people wanted to play a more proactive role in their world.

Nearly the entire history of cinema — much of it targeted at consumers in this very age range — retroactively applies our relatively recent understanding of teenagers as a distinct developmental stage to its young characters, and “Teenage” suggests how famous historical and literary figures (from Marie Antoinette to Romeo and Juliet) might have actually been perceived in their time. Still, 77 minutes is hardly adequate to cover the breadth of the four decades in question, and the film alternates between elegant transitions and confusing stretches as it tries to address everything from promiscuous, free-wheeling American flappers and “victory girls” to the ultra-organized, hyper-disciplined Boy Scouts and Hitler Youth.